1. Field of the Invention
The present invention relates to face masks for use in delivering respiratory gasses to a patient under positive pressure including such masks for use in treating sleep apnea or for other conditions requiring non-invasive positive pressure ventilation.
2. Background
The most effective and frequent therapy for obstructive sleep apnea is application of continuous positive airway pressure (CPAP). For such therapy, a patient is fitted with a tight fitting mask connected through an airway to a blower which supplies air to the patient's nasal passages or the nasal passages and mouth at a slight positive pressure. The application of the slight positive pressure is immediately effective in reversing the airway obstructions associated with obstructive sleep apnea. Although the therapeutic results of nasal CPAP are often dramatic and immediate, it is only effective when used properly and on a regular basis. Failure to apply nasal CPAP for even a single night results in recurrence of hypersomnolence the next day resulting from sleep apnea.
Problems associated with wearing existing masks or positive airway pressure delivery systems during periods of attempted sleep are sufficient to deter many patients from continuing CPAP therapy. Some problems include excessive noise and irritation resulting from leaks around improperly fitting masks or general discomfort caused by the design of the mask or the CPAP delivery system. Leakage of air between the mask and the face often allows air to blow on the eyes which wakes the patient and/or substantially irritates the eyes.
Most respiratory masks have integrally formed seals in the form of flexible or pliable flanges, cushions, pillows or the like extending around their outer periphery to form a seal between the mask and the face of the wearer. See for example the masks shown and described in U.S. Pat. Nos. 5,265,595 and 6,192,886. The seals are designed to prevent air from leaking through the interface between the mask and the wearer's face. However, patient movement and variations in the contours of different wearers' faces make it difficult to maintain a complete seal with existing face masks.
There remains a need for a respiratory mask for supplying gas to a patient under pressure which incorporates a seal which readily conforms to varying contours of wearer's to prevent leaks.